Damper with floating piston bleed channel

Abstract

A damper system for a vehicle is provided that includes a pressure tube and a piston assembly separating the pressure tube into first and second working chambers. A frequency dependent damper assembly, coupled to a piston rod at a position below the piston assembly, includes a plunger sleeve that is longitudinally moveable to transmit an adaptive force to a first valve assembly mounted to the piston assembly. The frequency dependent damper assembly includes first and second accumulation chambers that are separated by a floating piston. A second valve assembly, carried on the floating piston, controls fluid flow between the second accumulation chamber and the second working chamber. A bleed channel in the floating piston allows fluid flow between the first and second accumulation chambers, which reduces the adaptive force the plunger sleeve applies to the first valve assembly during high frequency, low velocity rebound inputs.

What is claimed is: 
     
       1. A damper system for a vehicle comprising:
 a pressure tube containing a hydraulic fluid; 
 a piston rod extending within the pressure tube along a longitudinal axis; 
 a piston assembly slidably fitted in the pressure tube for movement along the longitudinal axis, the piston assembly coupled to the piston rod and separating the pressure tube into a first working chamber and a second working chamber, the piston assembly including a first valve assembly that controls fluid flow between the first working chamber and the second working chamber; and 
 a frequency dependent damper assembly including a damper housing coupled to the piston rod, a plunger sleeve that is longitudinally moveable relative to the damper housing along the longitudinal axis between a rest position and an engaged position, a floating piston slidable relative to the damper housing for movement along the longitudinal axis between a seated position and an unseated position, the floating piston separating a first accumulation chamber of the frequency dependent damper assembly from a second accumulation chamber of the frequency dependent damper assembly, the first accumulation chamber being fluidly connected to the first working chamber and the second accumulation chamber being fluidly connected to the first accumulation chamber by a bleed channel in the floating piston, a plunger chamber disposed between the damper housing and the plunger sleeve that is fluidly connected to the first accumulation chamber, and a second valve assembly carried on the floating piston such that the second valve assembly moves longitudinally with the floating piston and controls fluid flow between the second accumulation chamber and the second working chamber, 
 wherein an increase in pressure within the plunger chamber creates an adaptive force on the plunger sleeve that moves the plunger sleeve longitudinally towards the piston assembly to the engaged position, the plunger sleeve contacting the first valve assembly in the engaged position to transmit the adaptive force to the valve assembly and increase resistance of the valve assembly to opening. 
 
     
     
       2. The damper system of  claim 1 , wherein the frequency dependent damper assembly includes an end plate mounted to the damper housing, the end plate including at least one channel that is disposed in fluid communication with the second accumulation chamber and the second working chamber. 
     
     
       3. The damper system of  claim 2 , wherein the second valve assembly includes at least one plate that is resilient and positioned longitudinally between the floating piston and the end plate, the at least one plate of the second valve assembly contacting the end plate when the floating piston is in the seated position and the at least one plate of the second valve assembly being longitudinally spaced away from the end plate when the floating piston is in the unseated position. 
     
     
       4. The damper system of  claim 3 , wherein the at least one plate of the second valve assembly includes at least one bleed port disposed in fluid communication with the at least one channel in the end plate that allows fluid to bleed out of the second accumulation chamber and into the at least one channel when the floating piston is abutting the end plate in the seated position. 
     
     
       5. The damper system of  claim 4 , wherein the piston rod includes a passage extending between the first working chamber and the first accumulation chamber. 
     
     
       6. The damper system of  claim 5 , wherein the frequency dependent damper assembly includes a check valve in the damper housing that controls fluid flow entering the first accumulation chamber from the passage in the piston rod. 
     
     
       7. The damper system of  claim 6 , wherein a first fluid flow path is defined during the rebound stroke of the piston assembly when fluid pressure in the first accumulation chamber is greater than the fluid pressure in the second accumulation chamber moving the floating piston to the seated position, the first fluid flow path extending from the first working chamber, through the passage in the piston rod, through the check valve, through the first accumulation chamber, through the bleed channel in the floating piston, through the second accumulation chamber, through the at least one bleed port in the at least one plate of the second valve assembly, through the at least one channel in the end plate, and out into the second working chamber. 
     
     
       8. The damper system of  claim 7 , wherein a second fluid flow path is defined during a rebound stroke of the piston assembly when fluid pressure in the first accumulation chamber is less than or equal to the fluid pressure in the second accumulation chamber and the floating piston is in the unseated position, the second fluid flow path extending from the first working chamber, through the passage in the piston rod, through the check valve, through the first accumulation chamber, through the bleed channel in the floating piston, through the second accumulation chamber, between the at least one plate of the second valve assembly and the end plate, through the at least one channel in the end plate, and out into the second working chamber. 
     
     
       9. The damper system of  claim 8 , wherein a third fluid flow path is defined during the compression stroke of the piston assembly when fluid pressure in the second accumulation chamber is greater than the fluid pressure in the first accumulation chamber moving the floating piston to the unseated position, the third fluid flow path extending from the second working chamber, through the at least one channel in the end plate, through the second accumulation chamber, through the bleed channel in the floating piston, through the first accumulation chamber, through the check valve, through the passage in the piston rod, and out into the first working chamber. 
     
     
       10. The damper system of  claim 8 , wherein the bleed port in the at least one plate of the second valve assembly has a cross-sectional area that reduces a volumetric flow rate of the hydraulic fluid traveling along the second fluid flow path relative to the first fluid flow path. 
     
     
       11. The damper system of  claim 8 , wherein the bleed port in the at least one plate of the second valve assembly has a cross-sectional area of 0.1 to 3.0 square millimeters. 
     
     
       12. The damper system of  claim 1 , wherein fluid flow through the bleed channel in the floating piston has a cross-sectional area that limits a volumetric flow rate of the hydraulic fluid traveling between the first and second accumulation chambers to provide reduced dampening at frequencies above 6 Hertz and velocities below 0.02 meters per second. 
     
     
       13. The damper system of  claim 1 , wherein the bleed channel in the floating piston has a cross-sectional area of 0.1 to 3.0 square millimeters. 
     
     
       14. The damper system of  claim 1 , wherein at least one aperture extends through the damper housing to fluidly connect the first accumulation chamber and the plunger chamber. 
     
     
       15. A damper system for a vehicle comprising:
 a pressure tube; 
 a piston assembly slidably fitted in the pressure tube that separates the pressure tube into a first working chamber and a second working chamber, the piston assembly including a first valve assembly that controls fluid flow between the first working chamber and the second working chamber; and 
 a frequency dependent damper assembly including a damper housing coupled to the piston assembly, a plunger sleeve that is longitudinally moveable relative to the damper housing between a rest position and an engaged position, a floating piston slidable relative to the damper housing for movement along the longitudinal axis between a seated position and an unseated position, the floating piston separating a first accumulation chamber of the frequency dependent damper assembly from a second accumulation chamber of the frequency dependent damper assembly, the first accumulation chamber being fluidly connected to the first working chamber, the second accumulation chamber being fluidly connected to the first accumulation chamber by a bleed channel in the floating piston, a plunger chamber disposed between the damper housing and the plunger sleeve that is fluidly connected to the first accumulation chamber, and a second valve assembly carried on the floating piston such that the second valve assembly moves longitudinally with the floating piston and controls fluid flow between the second accumulation chamber and the second working chamber, 
 wherein an increase in pressure within the plunger chamber creates an adaptive force on the plunger sleeve that moves the plunger sleeve longitudinally towards the piston assembly to the engaged position, the plunger sleeve contacting the first valve assembly in the engaged position to transmit the adaptive force to the valve assembly and increase resistance of the valve assembly to opening. 
 
     
     
       16. The damper system of  claim 15 , wherein the frequency dependent damper assembly includes an end plate mounted to the damper housing, the end plate including at least one channel that is disposed in fluid communication with the second accumulation chamber and the second working chamber. 
     
     
       17. The damper system of  claim 16 , wherein the second valve assembly includes at least one plate that is resilient and positioned longitudinally between the floating piston and the end plate, the at least one plate of the second valve assembly contacting the end plate when the floating piston is in the seated position and the at least one plate of the second valve assembly being longitudinally spaced away from the end plate when the floating piston is in the unseated position. 
     
     
       18. The damper system of  claim 17 , wherein the at least one plate of the second valve assembly includes at least one bleed port disposed in fluid communication with the at least one channel in the end plate that allows fluid to bleed out of the second accumulation chamber and into the at least one channel when the floating piston is abutting the end plate in the seated position. 
     
     
       19. A frequency dependent damper assembly for attachment to a piston rod of a vehicle shock absorber having first and second working chambers, the frequency dependent damper assembly comprising:
 a damper housing; 
 a floating piston retained on or in the damper housing, the floating piston being longitudinally moveable relative to the damper housing between a seated position and an unseated position, the floating piston separating a first accumulation chamber of the frequency dependent damper assembly from a second accumulation chamber of the frequency dependent damper assembly, the first accumulation chamber being fluidly connected to the first working chamber and the second accumulation chamber being fluidly connected to the first accumulation chamber; 
 a valve assembly carried on the floating piston such that the second valve assembly moves longitudinally with the floating piston, the valve assembly positioned to control fluid flow between the second accumulation chamber and the second working chamber, and 
 an end plate mounted to the damper housing, the end plate including at least one channel, disposed in fluid communication with the second accumulation chamber and the second working chamber, that is opened and closed by the valve assembly, 
 wherein the distance between the end plate and the valve assembly changes when the floating piston moves longitudinally between the seated and unseated positions. 
 
     
     
       20. The damper system of  claim 19 , wherein the second valve assembly includes at least one plate that is resilient and positioned longitudinally between the floating piston and a lip on the end plate, the at least one plate of the second valve assembly contacting the lip of the end plate when the floating piston is in the seated position and the at least one plate of the second valve assembly being longitudinally spaced away from the lip of the end plate when the floating piston is in the unseated position.